Add description to usage
Add description to usage

Signed-off-by: Mrunal Patel <d389837b018b67489df74a2c5f0aca13aaed44b6@gmail.com>

wking/ocitools-v2,hmeng-19/ocitools,opencontainers/runtime-tools,opencontainers/runtime-tools,wking/ocitools-v2,liangchenye/ocitools,opencontainers/ocitools,liangchenye/ocitools,opencontainers/ocitools,hmeng-19/ocitools